How can you seal a window permanently?

Question

like so little kids cant get out and fall?

Answer 1

you can put safety bars on the outside.  This way, you can still use your window.  If you don't want to have bars on you windows, use nails.  This way, you can reverse the process, and i doubt the kids will pry the nails out if you do it well.  

Answer 2

Hardware stores sell locks that s***w on the frames to keep it closed.

Answer 3

Depending on the window, you can nail it shut; you can seal it with a caulking compound; you can glue it shut.

I do not recommend glue as you may wish to be be able to open it at some future date.

The caulking will hold it shut, but will take a bit of effort to remove it, and the nail can be pulled out.

Also you can use a wooden strip in the correct place to prevent the window from being opened.